Medical studies reported recently have associated certain gaseous constituents of the human breath with specific types of diseases, and have addressed the importance of diet, dental pathology, smoking, etc, on determining the physiological levels of the marker concentrations in exhaled breath. Inflammation and oxidative stress in the lungs can be monitored by measuring the changes in the concentration of the following gases: NO (which has been widely studied as a bio-marker), and related products NO2-(nitrite); NO3-(nitrite); exhaled CO (also a marker for cardiovascular diseases, diabetes, nephritis, bilirubin production); exhaled hydrocarbons of low molecular mass, such as ethane, n-pentane; ethylene, isoprene (hydrocarbon affected by diet with is a marker for blood cholesterol levels); acetone, formaldehyde; ethanol; hydrogen sulfide, carbonyl sulfides, and ammonia/amines. For example, measurements of exhaled ammonia may differentiate between viral and bacterial infections in lung diseases to justify use of antibiotics.
Various sensors have been developed measuring these metabolites. Examples are described in, for example, U.S. Pat. No. 7,017,389, the entire contents of which are incorporated herein by reference. There is a continuing need for improvements in diagnostic tool breath analyzers that can provide, for example, a first detection device for fast and early diagnosis of medical conditions.